Study On The Adsorption Behavior And Mechanism Of Modified Waste Rock To Arsenic And Fluorine In Mineral Processing Wastewater

Arsenic and fluorine pollution of water resources is a problem facing the world environment,water containing arsenic and fluorine will pose a serious threat to human health,researchers around the world have done a lot of research to remove arsenic and fluorine in water,reduce the harm to the human body.Among the many methods to remove arsenic and fluorine in water body,adsorption method has become the most widely used arsenic and fluorine co-removal method because of its advantages of small pollution,simple operation,fast adsorption speed and many kinds of adsorbents.Based on the research object of mining stripping waste rock and polymetallic ore dressing wastewater of Yunnan Hualian Zinc&Indium Stock Co.,Ltd,the optimum modification conditions of waste rock were determined by modification test,and the adsorption properties of arsenic and fluorine in wastewater were studied,and the possible mechanism of arsenic and fluorine removal was put forward.The main research contents are as follows:?1?For investigating the physical and chemical properties of waste rock,the waste rock was characterized by XRD?XRF?SEM?BET and other means,and the main contents of waste rock were determined as oblique chlorite,illite,Muscovite and so on.The surface of waste rock is smooth,it is layered structure,and the layer and layer are closely overlapped.71.37%of the raw waste rock with particle size greater than0.9mm and the specific surface area is 1.169 m²/g.?2?In order to expand the adsorption capacity of waste rock,the effects of modified salt species,molar ratio of medicament,aging time of modified liquid,ratio of modified liquid to solid and modification temperature on the adsorption effect of modified waste rock were studied by modification condition experiment.The experimental results show that the optimum salt type of modifier is Al2?SO4?3,the molar ratio of reagent OH^-to Al³⁺is 6.4,the modification effect of liquid is the best,the ratio of liquid to solid is 1:63,the temperature influence is small,and the modification requirement can be achieved at room temperature.?3?By using the modified waste rock,the effect of waste stone particle size,dosage,adsorption temperature and waste water p H on arsenic removal and fluorine removal was studied.It was found that the finer the waste rock particle size and the more dosage under other conditions,the higher the removal rate of arsenic and fluorine;the temperature effect of adsorption process was less,and the wastewater p H was the best in neutral condition.the adsorption reaction was 60 min after the particle size of waste rock was 75?m?45?m?the dosage was 10 g/L?the adsorption temperature was25?and the p H value of wastewater was 7?initial p H?.the adsorption capacity of arsenic was 0.0461 mg/g,the adsorption capacity of fluorine was 0.427 mg/g,and the arsenic removal rate and fluoride removal rate reached 98.13%and 86.13%,respectively.?4?The fitting results of kinetic and thermodynamic models show that the fitting degree of arsenic removal reaction is higher by the second order kinetic equation,and the isothermal model Langmuir model and Freundlich model can describe the arsenic removal reaction process better,which indicates that the process of arsenic removal by waste rock adsorption should be a chemical adsorption-based process.Fluorine removal reaction data with the second-order kinetic equation fitting degree is much higher than the first-order kinetic fitting degree,isothermal model defluorination reaction process with Langmuir model fitting effect is better.The results show that the adsorption capacity of modified waste rock to arsenic in wastewater is stronger than that of fluorine,and the adsorption rate is faster.?5?By SEM?XPS and so on,the microscopic changes before and after the modification and adsorption of waste rock were discussed.The results showed that the interlayer spacing became larger,the whole was loose,and the pore size area increased.The surface electrical properties of waste rock were changed from negative to positive,and it was easier to react with negative ions such as H₂AsO₄^-?AsO₄^3-?HAsO₄^2-and F^- in water.Arsenate roots and fluorine ions in the wastewater after adsorption replaced the-OH,ligand exchange on the waste rock surface.The mechanism of adsorption is ligand exchange and electrostatic adsorption.